Excited State Intramolecular Proton Transfer (ESIPT)-Based Sensor for Ion Detection

Area of Science:

• Organic Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Developing selective chemosensors for ion detection is crucial in environmental and biological monitoring.
• Imidazole derivatives offer versatile scaffolds for designing fluorescent probes.
• Excited-state intramolecular proton transfer (ESIPT) is a photophysical process enabling sensitive fluorescence detection.

Purpose of the Study:

• To synthesize a C-2 and C-5 substituted imidazole derivative for selective ion sensing.
• To investigate the molecule's photophysical properties and its response to various analytes.
• To establish the detection limits and sensing mechanism for fluoride and cyanide ions.

Main Methods:

• One-pot, two-step synthesis of the imidazole-based sensor.
• Spectroscopic analysis (fluorescence, UV-Vis) to study ion interactions.
• Nuclear Magnetic Resonance (¹H-NMR) spectroscopy to elucidate the sensing mechanism.
• Time-resolved fluorescence decay measurements.
• Application on paper test strips for solid-state sensing.

Main Results:

• The synthesized imidazole molecule exhibits ESIPT, leading to light emission.
• Selective fluorometric and colorimetric detection of fluoride (F^-) and cyanide (CN^-) ions was achieved.
• Detection limits were determined as 9.22 μM for F^- and 11.48 μM for CN^-.
• ¹H-NMR studies confirmed proton abstraction by F^- and CN^- ions, indicating a distinct sensing mechanism.
• Successful application on paper test strips demonstrated practical utility.

Conclusions:

• The developed imidazole sensor provides a sensitive and selective method for detecting fluoride and cyanide ions.
• The ESIPT mechanism and proton abstraction are key to the sensor's response.
• The sensor's solid-state application on test strips highlights its potential for portable and rapid ion analysis.